Method and apparatus for flexible manufacturing a discrete curved product from feed stock

ABSTRACT

An apparatus for manufacturing a discrete curved product from a feed stock includes a source of heat that is adapted to impose a focused beam of light on at least one surface of a work piece to cause the surface of the work piece to expand and thereby move in the general direction of the heat source so as to impart a predetermined radius of curvature to the work piece. In addition, a method of manufacturing a discrete curved product from feed stock is also disclosed.

[0001] This application is a divisional of U.S. Ser. No. 09/900,075filed Jul. 6, 2001, which claims priority to and all benefits from theco-pending provisional application having U.S. Serial No. 60/216,082filed Jul. 6, 2000 and entitled Method and Apparatus for FlexibleManufacturing a Discrete Curved Product from a Continuous Feed Stock.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates, generally, to a method andapparatus for flexible manufacturing and, more specifically, to a methodand apparatus for flexible manufacturing a discrete curved part fromfeed stock.

[0004] 2. Description of the Related Art

[0005] There are numerous parts, components, and sub-components thatmust be subjected to one or more manufacturing steps to impart apredetermined curvature thereto. These manufacturing steps typicallyrequire the use of hard tooling which can include multiple progressivedies, cold heading operations, tube bending operations as well as theneed for other, associated components manufactured, for example, viaplastic injection molding operations or the like. This tooling andrelated hardware as well as the batch type processing of suchmanufacturing operations ultimately have a significant impact on thecost of the manufactured part.

[0006] Curved parts, components, and sub-components are commonlyemployed in various automotive applications. As examples only, and notby way of limitation, such curved parts, components and subcomponentsmay be found in automotive seat frames, seat backs, brake lines, andother various structural elements which embody a bend in any way. Onespecific example includes automotive windshield wiper assemblies. Morespecifically, it is known to employ a single, elongated, curved,homogeneous strip that forms a spring “backbone” of the windshield wiperassembly. Such windshield wiper assemblies are sometimes referred to as“beam blade” type windshield wiper assemblies. The beam blade backboneis made from spring steel and may taper both in width and thickness fromits center toward its free ends or tips. The backbone has a connectingformation at a central position for connection to a reciprocally drivenarm. The arm applies a downward force and moves the blade assemblyacross the windshield. The backbone is curved along a plane that issimilar to the plane of curvature as that defined by the windshield. Awiper element is secured to the backbone. The thickness and width of thebackbone and its radius of curvature are preferably matched at everypoint along the length of the backbone so that the backbone will providea force per unit length distribution in a longitudinal direction whichincreases toward both tips of the windshield wiper when the windshieldwiper is in use, pressed downward intermediate its ends onto either aflat or complexly curved surface. Beam blade windshield wiper assemblieshave the advantage of a lower profile as compared with tournament stylewiper assemblies, consist of fewer parts and are considered to beaesthetically pleasing.

[0007] While such beam blade type windshield wiper assemblies have manydesirable features and advantages, they can be difficult to manufactureand, due to the hard tooling required to shape, cut and curve thebackbone, relatively expensive when compared with other conventionalwindshield wiper assemblies known in the related art.

[0008] However, the present invention overcomes these difficulties inthe related art in a method and apparatus for flexible manufacturing adiscrete curved part, such as the backbone of a beam blade windshieldwiper assembly, from a feed stock. But, from the description thatfollows, those having ordinary skill in the art will appreciate that themethod and apparatus of the present invention may be used to manufactureany discrete, curved part from a feed stock and that the invention is inno way limited to the particular application referred to above ordescribed in greater detail below. Thus, the context of a beam bladetype windshield wiper assembly as described herein is merely for examplepurposes to further illustrate the present invention, and not for anylimiting purpose.

SUMMARY OF THE INVENTION

[0009] The present invention overcomes the deficiencies in the relatedart in a method and apparatus for flexible manufacturing a discretecurved product from a feed stock. The apparatus includes a source ofheat that is adapted to impose a focused beam of heat on at least onesurface of a work piece to cause the surface of the work piece to expandand thereby move in the general direction of the heat source and imparta predetermined radius of curvature to the work piece.

[0010] A method of manufacturing a discrete curved product from a feedstock is also disclosed and includes the steps of providing a focusedbeam of heat on at least one surface of a work piece to cause thesurface of the work piece to expand and thereby move in the generaldirection of the heat source and thereby impart a predetermined radiusof curvature to the work piece.

[0011] Operator interface in a production line employing the method andapparatus of the present invention is minimal and consists, primarily,of monitoring the status of the production line and the product qualitybeing produced, rather than control of the process. Ideally, theproduction line includes few or no hard tools, but rather, is primarilysoftware controlled to allow changes and modifications to the endproduct's “on the fly.” Thus, as will be described in greater detailbelow, a production line employing the method and apparatus of thepresent invention is “virtually tooled” and can produce any number ofdifferent parts without stopping or even slowing the manufacturingprocess. However, those having ordinary skill in the art will appreciatefrom the description that follows that, while the reduction in the useof hard tooling is an overall, general goal of the method and apparatusof the present invention, some hard tooling may still be employed in anygiven production line without deviating from the scope of the inventionas defined in the appended claims.

[0012] Similarly, in the preferred embodiment contemplated by theinventors, the production line employing the method and apparatus of thepresent invention includes a digital signal processing computer having aneural network including a design database with predeterminedmanufacturing settings that control the overall process to produce theend product. Thus, the method and apparatus of the present inventionoffer numerous advantages over the traditionally hard-tooled productionlines known in the related art. Most notably, these advantages includethe ability to continuously flow process the working material whilereducing or eliminating, as much as possible, the batching processes inthe production of a part, component or sub-component. This advantageresults in reduced costs, waste and labor expenses. The method andapparatus of the present invention also provides improvements ininventory turns and more efficient utilization of raw materials.Furthermore, the cost to manufacture and build a production lineemploying the method and apparatus of the present invention is less thanthe cost to tool a family of parts employed to manufacture products,such as windshield wiper assemblies, automotive seat frames, seat backs,brake lines, bent tubular products and other various structural elementsthat embody a bend in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Other advantages of the present invention will be readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein:

[0014]FIG. 1 is a perspective view of a beam blade wiper assembly havinga backbone made using the method and apparatus of the present invention;

[0015]FIG. 2 is a schematic representation of a production line formanufacturing a discrete, curved part from feed stock;

[0016]FIG. 3 is a schematic view of a wound coil of spring steel;

[0017]FIG. 4 is a schematic representation of a cold rolling mill;

[0018]FIG. 5 is a schematic representation of a width profiling station;

[0019]FIG. 6 is a schematic representation of a curvature forming andheat treat station;

[0020]FIG. 7 is a schematic representation of a cutting station;

[0021]FIG. 8 is a schematic representation of a part cleaning andpainting station; and

[0022]FIG. 9 is a flow chart illustrating each step of a flexiblemanufacturing process of the present invention as it is applied to themanufacture of a beam blade windshield wiper assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0023] The method and apparatus of the present invention will bedescribed in greater detail below in connection with one possible usefor manufacturing a beam blade windshield wiper assembly. However, asnoted above, those having ordinary skill in the art will appreciate fromthe description that follows that the method and apparatus of thepresent invention may be employed in connection with a number of diverseproducts and is in no way limited to the example described herein. Tothis end, a representative example of a beam blade windshield wiperassembly is generally indicated at 10 in FIG. 1, where like numbers areused to designate like structure and method steps throughout thedrawings. The beam blade windshield wiper assembly 10 includes abackbone 12 and a wiper element 14. The beam blade windshield wiperassembly 10 is controlled and driven by a spring-loaded arm, a portionof which is illustrated in both continuous and phantom lines at 16 inFIG. 1. The beam blade windshield wiper assembly 10 is mounted adjacentthe windshield (not shown) of a vehicle and pivotally driven to impartreciprocating motion to the beam blade wiper assembly 10 across thewindshield, as commonly known in the art. The backbone 12 is connectedto the arm 16 by a coupler, generally indicated at 18, which acts toreleasably connect the wiper assembly 10 to the spring loaded wiper arm16.

[0024] The elongated backbone 12 has a longitudinal beam lengthextending between first and second ends 20, 22. The beam length definesa median line 24 extending along the beam length. The coupler 18 islocated at an intermediate position, commonly at the longitudinalcenter, between the first and second longitudinal ends 20, 22. However,those having ordinary skill in the art will appreciate that the couplercan be located biased toward one end, 20, or the other, 22. The backbone12 is made of resiliently flexible material that applies a force fromthe spring loaded wiper arm 16 through the coupler 18 along thebackbone's length to the first and second longitudinal ends 20, 22. Thebackbone 12 is typically made of a single, integral piece of material.

[0025] The backbone 12 includes an upper surface 26 and an opposedmounting surface 28 with first and second sides or edges 30, 32extending therebetween. Preferably, the wiper element 14 is mechanicallyattached, bonded, chemically attached, or otherwise adhered to themounting surface 28 of the backbone 12 and extends for a substantialportion of the longitudinal beam length. The cross-section of thebackbone 12 is generally rectangular making the first and second sides30, 32 generally perpendicular to both the upper surface 26 and mountingsurface 28. However, the cross-section of the backbone 12 may includeany suitable geometric shape. The backbone 12 has a width “W” definedalong a width line drawn between the first and second sides 30, 32 andperpendicular to the median line 24. The thickness of the backbone 12 isdefined by an imaginary line t extending perpendicular to the widthbetween the upper surface 26 and mounting surface 28. In general, thewidth and thickness of the backbone may be consistent or the backbonemay vary in width and/or thickness along its longitudinal length.

[0026] The backbone 12 is curved longitudinally with a predeterminedfree form shape or radius of curvature that, when operatively disposed,extends in the general direction of the plane of curvature of thewindshield (hereinafter “windshield curvature”). An x-y plane is definedby a cross section taken longitudinally along the median line 24 andthrough the backbone 12 and wiper element 14, with the x-axis extendingtangentially to the median line 24 at the center of the backbone 12 andthe y-axis extending through the cross-section of the backbone 12 andwiper element 14. A z-axis extends perpendicular to the x-y plane in thedirection of a width line drawn at the center or connecting portion ofthe backbone 12 to the coupler 18. The curvature of the backbone 12 inthe x-y plane may be symmetrical or asymmetrical depending on the forcerequirements and the contour of the windshield. The flexible, free form,pre-curved backbone 12 flattens out, or the curvature is reduced, suchthat the backbone will conform when the wiper arm 16 applies a forcethereto on a windshield. Thus, the backbone 12 must have adequatefree-form curvature to ensure a good force distribution on windshieldshaving various curvatures and to effect proper wrapping about thewindshield.

[0027] In connection with such beam blade windshield wiper assemblies(as well as numerous other products) there is a need to manufacture thelong, thin, curved backbone 12 in a manner capable of supplying a highvolume automotive application in an efficient, cost effective manner.Furthermore, there may be a need to manufacture such a component thatmay have a tapered shape in either or both of its width W or thicknesst. The present invention includes a method and apparatus which may beemployed to manufacture such a component and which may form a part of aflexible production line, generally indicated at 40 in FIG. 2. Ingeneral, the flexible production line 40 may be employed to manufactureany number of discrete, curved components or parts. However, theproduction line 40 will be described in the context of manufacturing acurved, backbone of a beam blade type windshield wiper assembly 10 ofthe type illustrated in FIG. 1. Those having ordinary skill in the artwill appreciate from the description that follows that the method andapparatus of the present invention may be employed to manufacture anynumber of curved parts, components and/or sub-components and that thepresent invention is not limited to automotive applications, in general,nor windshield wiper assemblies, in particular. To this end, such aproduction line 40 may include a source of a work piece, such as a woundcoil of spring steel, generally indicated at 42 (FIGS. 2 and 3); a coldrolling mill, generally indicated at 44 (FIGS. 2 and 4); a widthprofiling station, generally indicated at 46 (FIGS. 2 and 5); acurvature forming and heat treat station, generally indicated at 48(FIGS. 2 and 6); a cutting station, generally indicated at 50 (FIGS. 2and 7) and a part cleaning and painting station, generally indicated at52 (FIG. 8). Each stage of the production line 40 will now be describedin greater detail below.

[0028] Referring specifically to FIG. 3, and for purposes ofmanufacturing the backbone 12, the wound coil of steel 42 is preferablya medium carbon-manganese spring steel, for example SAE 6150 or otherlow alloy steels in the medium carbon range. The coil 42 is oscillatewound off the master coil and is butt welded and cold cross rolled atthe joining points. The butt weld area is annealed. The coil 42 includesa take up loop, schematically indicated at 54. The take up loop 54 isweighted to produce a back tension in the material or work piece,schematically illustrated at 56, before it enters the first operation.The coil 42 may also include a laser vision system 55 (FIG. 4) installedover the material so that the butt joined area may be identified. Thelocation of the butt joined areas is sent down a serial bus so that noparts will be made from joined material.

[0029] From the coil 42, the steel working material 56 has a light filmof oil rolled or sprayed onto both sides of it (schematically indicatedat 57 in FIGS. 4 and 9) and is then guided into the cold rolling mill 44(FIG. 4). The rolling mill 44 is designed to condition the work piece byimparting a predetermined constant or variable thickness t thereto. Tothis end, the cold rolling mill 44 may include fixed, tapered andvertical guides and programmable side rollers (schematically representedat 59). The rolling mill 44 includes a pair of opposed, rollers 58, 60which are rotatable about axes disposed generally transverse to thedirection of travel of the working material 56 as it flows through themill 44 and between the rollers 58, 60. At least one of the rollers 58,60 is movable in a direction perpendicular to the path of the workingmaterial 56 through the mill 44 and toward or away from the otherroller. More specifically, and as illustrated in the preferredembodiment of FIG. 4, the roller 60 is movably mounted to a hydraulicactuator, schematically indicated at 62. A pair of roll sensorassemblies, 64, 66, are mounted across corners to measure the separationbetween the rollers 58, 60 at 0.2 mm linear position increments of thematerial 56. The sensors 64, 66 form a part of a control system thatwill be described in greater detail below.

[0030] In the representative example disclosed herein, it is desiredthat the backbone 12 taper in both width and thickness. The width of thebackbone 12 will be addressed at the width profiling station 46described in greater detail below. A tapered thickness is imparted tothe steel working material 56 at the rolling mill 44. Thus, in thepreferred embodiment, the mill 44 has high stiffness, without back uprollers, because the material width of the backbone is less than 30 mm.To the extent that the thickness of the backbone varies, the variance ofthe material 56 must be controlled to plus or minus 20 μm. The material56 is always reduced by at least 0.3 mm and can be reduced as much as1.1 mm. The cold rolling mill 44 may generally be of the type disclosedin U.S. Pat. No. 5,590,566 issued on Jan. 7, 1997 and entitled,“Apparatus for the Manufacturing of a Thin Metallic Strip”; and/or U.S.Pat. No. 5,875,672 issued on Mar. 2, 1999 and entitled, “Method andApparatus for Manufacturing Metallic Support Beams for Windscreen WiperBlade Assemblies.” Both of these patents are assigned to the assignee ofthe present invention. The disclosures of these patents are incorporatedherein by reference.

[0031] The driven rollers 58, 60 pull the material from the take up loop54. The actual outgoing material thickness may vary depending on thedesired operating parameters of the end product being manufactured, inthis example, the beam blade windshield wiper assembly. Thus, thematerial's thickness is also measured at 67 using a linear thicknessmeasuring device. The material's actual thickness is then compared tothe rolling mill's targeted thickness. Furthermore, an incremental shaftencoder, generally indicated at 68, is employed to measure the linearposition down the axis of the semi-formed part. The separation of therollers 58, 60 is controlled by a digital signal process controllerwhich receives feedback from the various sensors 64, 66, 67 and encoder68, as will be discussed in greater detail below.

[0032] Because of the tight thickness and thickness gradient tolerancesthat may be required to manufacture any given product, such as thebackbone 12, a program logic controller (PLC) cannot process theincoming sensor information within a desirable and acceptable timeinterval. Thus, a digital signal processing (DSP) computer that iscapable of processing the material thickness in real time as it is seenby the sensors, for example, 64, 66 which measure the amount ofseparation between the rollers 58, 60 and sensor 67 which measures thethickness of the material after it has passed through the rollers 58,60, is required to control the operation of the method and apparatus ofthe present invention. To this end, the digital system processingcomputer (schematically indicated at 71 in FIG. 9) employed with themethod and apparatus of the present invention also utilizes a neuralnetwork machine controlled program which is fed with various thicknessand position information so that adjustments in spacing between therollers 58, 60 can be made in real time thereby allowing the thicknessand thickness gradient tolerances to be held. In this way, the profileof the material 56 will be accurately modified so that the cold rollingmill 44 provides a semi-formed, continuous strip of metal, generallyindicated at 70, having a predetermined thickness that may vary alongthe length of the strip 70. The digital signal processing computer 71utilizing the neural network will be described in greater detail below.

[0033] Thereafter, any residual oil left on the semi-formed part 70 fromthe cold-rolling process may be removed as indicated at 69. Furthermore,a tensioner assembly, generally indicated at 72, is employed to ensurethat the semi-formed part 70 is kept under tension and to helpstraighten out the edge curvature of the material 70. The tensionerassembly 72 has two opposed rollers 74, 76 that are controlled usingservo drive motors. The torque generated by these rollers 74, 76 issufficient to continuously move the semi-formed material 70 therethroughand can produce enough torque to provide up to 30 percent of the pullingpower for the entire rolling process. The pulling force is sufficientenough to “pull the tail straight” on the semi-formed part 70, thusremoving the edge camber of the material. Programmable side rollers 59on the incoming side of the rolling mill 44 can also be employed to helplaterally move or resist the material movement, so as to help thetensioner assembly 72 straighten the edge camber. An ink-jet marker 73may be used to selectively mark a line on the semi-formed part 70 atpredetermined places therealong to designate the end/beginning of afully formed part as will be described in greater detail below. However,those having ordinary skill in the art will appreciate that numerousother repeatable marking techniques may be employed for this purpose.For example, and as an alternative to an ink jet mark, somepredetermined physical or geometric change in the material or materialthickness or surface of the work piece may be imparted to designate thebeginning and/or the end of a fully formed part.

[0034] The semi-formed continuous strip material 70 having a variablethickness is then transferred to the width profiling station, generallyindicated at 46 in FIGS. 2 and 5. A vision system 77 may be employed toidentify the starting point of each individual designated part (as notedby the ink jet mark or other marking technique) that enters this widthprofiling station 46. A linear encoder, generally indicated at 78,rechecks the length position on the part identified by the ink. Thewidth profiling station 46 includes a cutting station, generallyindicated at 80. More specifically, and as illustrated in the preferredembodiment, a twin-headed laser 82 is mounted over the semi-formed part70 and projects the focal position of the laser optics onto the part 70.To this end, the laser 82 is mounted at a predetermined, proper heightabove the part 70 to provide an optimum cut. The twin heads are placedapart so that the optics do not interfere with each other and so thatthey can cut the part 70 to a minimum width of 4 mm. In the preferredembodiment contemplated by the inventors, the cutting station 80 employsa 2.2 KW diode pumped Nd: YAG laser, equipped with a 50/50 laser beamsplitter. The laser is remotely mounted relative to the part 70 and thelaser power is provided to the work station 46 via two fiber-opticcables (not shown). Alternatively, the cutting station 80 mayincorporate a pair of CO₂ lasers, or any other suitable cutting source.

[0035] As indicated in FIG. 5, as the laser cuts the width of the part70, the scrap material, generally indicated at 84 is pulled down andaway from the part 70 so that it can be cut into small pieces fordisposal. In addition, the material 70 is notched, as indicated at 86 inFIG. 9, for purposes of mounting the coupler 18 to the backbone 12 asdescribed above. An overhead width laser measuring system, generallyindicated at 88, is employed to verify the actual width and positiondimensions of the part after it has been cut by the overhead laser 82.The measuring system 88 uses an overhead line laser beam 90 and anunderneath camera 92 to measure the projected shadow of the part width.In addition, another tensioner assembly, generally indicated at 94, isemployed to keep a light tension on the part in the width profilingstation 46 of the production line 40. However, in the preferredembodiment illustrated in this figure, the tensioner assembly 94includes only a single servo drive motor. The width profiled material orwork piece produced from the cutting station 46 is schematicallyrepresented at 96 in FIGS. 5 and 6.

[0036] In addition to the sensors and measuring system discussed aboveand illustrated in the figures, for any given curved component thatcould be manufactured using the method and apparatus of the presentinvention, there may be a need for additional, similar or even differentsensing and measuring systems to provide adequate feedback and controlof the overall process. For example, those having ordinary skill in theart will appreciate that a measuring system of the type described above,and generally indicated at 88 in FIG. 5 as well as additional sensors ofthe type described above and identified at reference numbers 67 and 68in FIG. 4 could be added to the flexible production line 40 after thetensioner assembly 72 and before the width profiling station 46 so thatadditional data regarding the relevant characteristics of the work pieceat this point in the process may be collected and used to control theoverall process. Thus, from the overall description of the method andapparatus of the present invention contained herein, those havingordinary skill in the art will appreciate that the number, type andpurpose of the sensors described herein is not exhaustive and thatadditional like devices could be employed throughout the productionline.

[0037] Following the cutting station 46, the newly profiled material 96is fed to the curvature forming and heat treatment station, generallyindicated at 48 in FIGS. 2 and 6. To this end, the position of thematerial 96 is again identified by the paint markings or predeterminedphysical, geometric change in the material thickness that indicates thepredetermined beginning and end of the backbone 12 which will ultimatelybe manufactured in this representative example. Furthermore, a shaftencoder 98 (FIG. 9) is employed to re-identify the predetermined lengthof the end product and a width re-identification laser sensor isemployed for determining the center of the final product. The stripmaterial 96 may be rotated 90° (see also 100 at FIG. 9) so that it isdisposed on one of its edges 30, 32. In essence and in this example, thematerial 96 is twisted 90°. The twisting is done in the elastic range ofthe material 96 so as to impart no additional residual stresses in thepart material. However, those having ordinary skill in the art willappreciate that rotation of the part is not critical to the invention.

[0038] Next, a curvature of predetermined radius is then permanentlyimparted to the material 96 between its predetermined beginning and endpoints (see 102 at FIG. 9). This predetermined radius of curvature isimparted to the material 96 by heating one surface 104 of the material96 so as to expand, but not necessarily melt, the material andthereafter immediately cooling the material (see 106, FIG. 9) in a rapidfashion. For this purpose, the apparatus of the present inventionincludes a first source of heat that is adapted to impose a focused beamof heat on at least one surface of a work piece. One preferredembodiment of a source of heat as contemplated by the inventors includesa laser that produces a diffuse beam of light directed toward at leastone surface of the work piece. Another preferred embodiment of the firstsource of heat is a water-cooled, plasma, infrared lamp that alsoproduces a beam of light directed toward at least one surface of thework piece. A suitable water-cooled, plasma, infrared lamp is availablefrom Vortek-Technologies who maintain a website at www.vortek.com. Thosehaving ordinary skill in the art will appreciate that there may be othersources of heat that could be employed in the method and apparatus ofthe present invention. All that is necessary is that the first source ofheat be capable of imparting a predetermined radius of curvature to thework piece as described in greater detail below. Accordingly, thepresent invention as hereinafter further described will be presented inthe context of a laser employed as the first source of heat.

[0039] To this end, one preferred embodiment of the method and apparatusof the present invention employs a laser, generally indicated at 108,that is focused on one surface 104 of the part 96. The laser 108 employsa diffused beam of oval or “line-like” configuration having a major axisextending transverse to the longitudinal axis and movement of thematerial 96. The oval shaped beam extends transverse to the surface ofthe work piece. Said another way, the beam of heat extends across, orsubstantially across, the entire width of the part. As noted above, thepower of the laser 108 is modulated and controlled so as, ideally, notto melt the surface 104 of the part 96 but rather to expand the surface104 of the material 96 upon which the beam impinges. As the one surfaceof the work piece expands, the work piece moves in the general directionof the heat source, in this case, the laser, thereby imparting apredetermined radius of curvature to the work piece. As the one surfaceof the work piece expands, it has been observed that this process causesthe material on that one surface to “gather” so as to impart the bend tothe work piece.

[0040] In the preferred embodiment, the laser is a 6 KW direct diodelaser 108 having an oval-shaped beam output with a length along itsmajor axis of approximately 12 mm and a length across its minor axis ofapproximately 1 mm. However, in the preferred embodiment, the beamshould be sized so that it extends across, or substantially across, thewidth of the surface that is being treated. The beam is scanned along apredetermined portion of the surface 104 of the material of each endproduct in the direction of the longitudinal axis of the material 96. Inthe embodiment illustrated here, the material 96 moves relative to thelaser beam. However, those having ordinary skill in the art willappreciate that the beam could be moved relative to the material.Similarly, while the backbone of the beam blade windshield wiperassembly described in detail herein may have a predetermined radius ofcurvature imparted thereto using a single source of heat that is scannedover the work piece in a single pass, those having ordinary skill in theart will appreciate that one or more sources of heat may be employed forany given application and that the work piece may be scanned by the beamof heat multiple times. Furthermore, where multiple sources of heat areemployed, those heat sources may be engaged at the same of variouspositions on the work piece and may be adapted to impose both focusedand defocused beams thereon.

[0041] In any event, immediately after it has been heated by the laser108, the surface 104 is cooled. This process may be achieved usingpassive or active cooling techniques. In the preferred embodiment, theexpanded surface 104 of the material is actively cooled using a vortexcooler 110. The vortex cooler 110 is located adjacent to the point ofimpingement of the laser on the surface 104 of the material 96. Thevortex cooler 110 is of the type manufactured by Exair Corporationlocated in Cincinnati, Ohio and having a website athttp://www.exair.com. However, those having ordinary skill in the artwill appreciate that any number of suitable cooling mechanisms commonlyknown in the art may be employed for this purpose.

[0042] While the material is being heated by the laser 108, it is fullyaustenized However, when it is cooled, the material attempts to returnto its original thickness but is cooled too rapidly for this to occur.This heating/cooling process results in material forces that impart acurvature to the material 96 along its longitudinal axis. At the sametime, the rapid cooling is sufficient to produce a thorough hardnessthat is an untempered martinsite at RC 58/60. Rapid cooling results in asurface and sub-surface strain on the area of the work piece that isbeing cooled. These strains are vectored in the general direction of theconstriction. It has been noted that, since the work piece is heatedadjacent to the area that is cooled, the heated material cannot sustaina resisting strain to oppose the strain produced in the cooled area. Inthis case, the surface of the area of the work piece that is beingcooled is pulled toward the area that is being heated thereby impartinga permanent predetermined radius of curvature to the work piece. Thecurvature forming and heat treatment station 48 may therefore include acurvature-sensing system as indicated at 112 in FIGS. 6 and 9 disposedas close to the laser 108 and vortex cooler 110 as possible.

[0043] The laser power is modulated to control the actual radius ofcurvature of the part being manufactured to the specified radius. Tothis end, the digital signal processing controller 71 for the overallsystem employs a neural network software system to control the processvariables, including the material thickness, width profiling, curvatureand thermal expansion properties. In one embodiment contemplated by theinventors, the neural network employed in connection with the productionline 40 may have one hundred or more nodes. Each node is defined by aweighted value and by connections to other nodes. Various weightedvalues may be used to simulate the nodes of a neural network, dependingon the part being manufactured in connection with the production line40, the type of material employed as well as a number of other factors.Thus, the exact network configuration and weighted values will varydepending on the specific application (e.g. type and metallurgicalmakeup of the material employed, thickness of the material, type andpower of the heat source, type of power supply, speed of the materialflowing through the production line 40 as well as the nature and thenumber of sensors employed in the production line 40).

[0044] The input nodes of the neural network receive digital voltagesignal data in a certain, real time, window. The nodes may be eitherevenly or non-linearly spaced in the time window. In any event, theneural network is deterministic, in that a given input will alwaysproduce the same output. In the example discussed herein, the neuralnetwork provides an output that indicates whether the thickness ofmaterial 70 produced at the rolling mill 44 is produced withinacceptable ranges; whether the width of the material 96 produced at thewidth profiling station 46 has been cut within acceptable levels;whether the curvature imparted to the material 124 in the curvatureforming and heat treat station 48 is within acceptable levels; andwhether the part 12 has been cut to its proper dimensions in the cuttingstation 50. The digital signal processing controller 71 adjusts variousparameters at each of these stations 44, 46, 48 and 50 by sending therequired control signals to various sensors 55, 64, 66, 67, 68, 73, 76,88, 98, 112 and 128 (FIG. 7), as well as possibly other sensors, whichcontrol the operations at each of these stations.

[0045] In this regard, the real time digital signal processingcontroller 71 performs the step of comparing parameters sensed by thesensors with the parameters stored in one or more look up tablescontained within the memory of the digital signal processing controller71. The contents and format of the look up tables will vary dependingupon a number of factors including, but not limited to, the type of partbeing manufactured, the material used to manufacture the part, itsthickness, the type of laser and power for the laser, etc. The contentsof any given look up table are determined during actual pre-productionprototyping experiments. Once an entry in the look up table is foundthat matches the parameters sensed by the various sensors and fed to thedigital signal processing controller 71, the controller compares theactual reading to the information contained in its look up tables andadjusts the necessary parameters to drive the actual readings sensed bythe sensors to the desired readings contained within the look up tables.This sophisticated control apparatus allows the rolling mill 44 as wellas the lasers 80 and 108 (and lasers 116, 118 and 126 described below)to adapt their power to make the backbone 12 to the desired dimensionsand material properties.

[0046] After the predetermined radius of curvature is imparted to thematerial 96, it is then heat-treated. Thus, the apparatus includes atempering station, generally indicated at 114 in FIG. 6. Morespecifically, the material 96 is then tempered back to a RC 46/50. Thosehaving ordinary skill in the art will appreciate that the temperingstation may include any suitable tempering device, such as traditionalinduction tempering devices as well as any other tempering devicescommonly known in the art. However, with respect to the embodimentsdisclosed herein, the tempering device is a second source of heatdisposed, preferably, in non-contacting relationship to the work piece.More specifically, the tempering device may include a laser thatimpinges a beam of light on the work piece thereby tempering it.Alternatively, the tempering device may include an infrared lamp, andpreferably a water-stabilized plasma infrared lamp.

[0047] Notwithstanding the various tempering devices that may beemployed for this purpose, in the preferred embodiment, tempering isaccomplished by the use of two, opposed direct diode lasers 116, 118that emit a pair of defocused laser beams 120, 122, respectively whichimpart the heat treatment. It is believed that, in the preferredembodiment, the tempering process should be done using a non-contactingmethod so as to not change the freeform curvature of the material 96that has been induced using the laser 108. Furthermore, because thespecific part curvature and its length may vary from end product to endproduct, the position of the tempering station 114 relative to thesurface of the material 96 must float in the vertical plane of thematerial's normal deflection movement. However, the focus of the beamsproduced by the opposed lasers 116, 118 on the opposed surfaces of thematerial 96 must be maintained at the proper distance to temper thematerial 96 to the specified hardness.

[0048] The material or work piece produced at the curvature-forming andheat-treat station 48 is schematically indicated at 124 in FIGS. 6 and7. This material 124 is now complete from a thickness, width, curvatureand heat treatment standpoint. It must now be cut to a predeterminedlength. Since the individual length and curvatures of various endproducts may vary, the position in space where the material 124 is cutmust also float in both the vertical plane (due to the part curvature)as well as to its longitudinal position (due to the length changes ofthe end products). Accordingly, in the preferred embodiment, it isbelieved that the material 124 must be cut using a non-contacting methodso as not to change the curvature in the part in the upstreamcurvature-forming and heat-treating station 48. At the same time, thematerial 124 may need to be edge-supported so as not to cause ashockwave to be sent back through the material upstream from the pointthat it is being cut. Accordingly, in the preferred embodiment, themethod and apparatus employs a cutting station 50 using a cutoff laser126. A coordinate measuring system, generally indicated at 128 in FIGS.7 and 9 is employed to determine the exact position and location of thematerial prior to cutting. In the preferred embodiment, the cutoff laser126 is controlled in the X, Y, and Z axes using the DSP controller 71and its neural network. A fixture, schematically indicated at 130, maybe used to support the material 124 on one or both of its edges 30, 32so that the part does not change its freeform curvature. To this end,and in the preferred embodiment, the cutoff laser 126 is supported upona robotic arm, generally indicated at 132 which controls the cutting ofthe material in the X, Y, and Z axes. In this way, a discrete backbone12 is formed.

[0049] The individual backbones 12 are now ready to be cleaned andpainted. However, prior to any painting or coating operation, thebackbones 12 may be subjected to additional heat treats includingannealing, quenching, and/or cooling of the backbones. Morespecifically, and as indicated in FIG. 9, the backbones 12 may besubjected to an end treatment 134. This may include, for example,forming a downwardly extending, cup shaped lip portion at either end ofthe backbone as indicated at 136 and 138 in FIG. 9. These lip portionseliminate sharp edges and act to receive the terminal ends of the rubberwiper elements 14 in the event that they extend the entire longitudinallength of the backbone 12. In any event, the backbones 12 are nextsubjected to a conventional powder-coating operation 140 (FIG. 9) at aclean and paint station 52 (FIG. 8). However, those having ordinaryskill in the art will appreciate that the backbone 12, or another partmanufactured using the method and apparatus of the present invention,may be subject to other post forming operations without departing fromthe scope of the invention. Because the backbone 12 forms the part of avisible windshield wiper system, its finish requirements are that of aclass A surface. Thus, the surfaces of the backbone 12 must be smoothfrom all previous operations and free of any sharp edges. Furthermore,the backbone must be free of any visible surface irregularities, whichmay sometimes appear as wavy marks. The edges of the backbone producedat the width profiling station 46 must be free of drowse and, to asomewhat lesser extent, the edge scallop marks which may be produced inthe laser cutting process which produces the width profile to thebackbone 12. The heat-treated surfaces of the backbone 12 must also befree of scale and should have minimal decarborization.

[0050] In the preferred embodiment, the backbone 12 will be clamped inthe part cleaning and painting station 52 and subjected to an acid dip143 which cleans the part as well as phosphate 144 and powder spray 146(FIG. 9). The sprayed backbone 12 will then be baked in a conventionalmanner as indicated at 148 in FIGS. 8 and 9. A coupler, of the typeindicated at 18 in FIG. 1, is then attached to the backbone 12 (see 150FIG. 9). This may include the steps of locating the backbone 12 in apredetermined position 158 and attaching the coupler 18 thereto to forma beam blade windshield wiper assembly as indicated at 152 on the flowchart of FIG. 9. Thereafter, a wiping element of the type indicated at14 in FIG. 1 will be mounted to the backbone 12 as indicated at 156 inFIG. 9. With reference primarily to FIG. 9, this may include the step oflocating the backbone 12 in a predetermined position (160), applying anadhesive such as glue to one surface of the backbone 12 (162),positioning the rubber wiping element 14 relative to the backbone 12 andapplying a sufficient pressure to adhesively attach the wiping element14 to the downwardly curved, arcuate surface of the backbone 12 (164).The adhesive is then allowed to cure (166). The assembly may also besubjected to a corona treatment or other surface energy producingprocess, as indicated at 154 in FIG. 9. Such a treatment involves theapplication of a high voltage to the backbone 12 at a low current. Thistreatment assists the bonding of the rubber wiping element 14 to thebackbone 12 via the adhesive. The assembly is thereafter available forpackaging, storage, and/or shipping, as is generally indicated at 168 inFIG. 9.

[0051] The method and apparatus of the present invention is adapted toaccommodate continuous flow of the working material 56, 70, 96 and 124from the payoff coil station 42 through the cutting station 50 whereinthe backbones 12 are ready for cleaning and painting at 52. A productionline 40 employing the method and apparatus of the present invention willideally run at 10 m/min. and, it is estimated that the coil will lastfor over 50 hours. Operator interface (schematically indicated by theacronym “HMI” for Human Machine Interface in FIG. 9) will be minimal andwill consist, primarily, of monitoring the status of the production line40 and the product quality being produced, rather than control of theprocess. The production line 40 may include a limited number of hardtools, but, ideally, is software controlled to allow changes andmodification to the end products “on the fly.” Ideally, the productionline 40 described above is “virtually tooled” which can produce anynumber of different parts without stopping or even slowing themanufacturing process. The production line 40 relies on a digital signalprocessing computer 71 employing a neural network having a designdatabase including predetermined manufacturing settings which controlthe overall process to produce the end product. Thus, the method andapparatus of the present invention offer numerous advantages over thetraditionally hard-tooled production lines known in the related art.Most notably, these advantages include the ability to continuously flowprocess the material while reducing or eliminating, as much as possible,batching processes in the production of a part, component orsub-component. This results in a reduction of costs, waste and laborexpenses. The method and apparatus of the present invention alsoprovides improvements in inventory turns and more efficient utilizationof raw materials. Furthermore, the cost to manufacture and build aproduction line 40 employing the method and apparatus of the presentinvention is less than the cost to tool a family of parts employed tomanufacture products, such as windshield wiper assemblies, known in therelated art.

[0052] As noted above, the method and apparatus of the present inventionmay be employed to manufacture any number of discrete, curved componentsor parts. And, while the method and apparatus of the present inventionhas been described in the context of manufacturing a curved, backbone ofa beam blade-type windshield wiper assembly, those having ordinary skillin the art will appreciate that the method and apparatus of the presentinvention may be employed to manufacture any number of curved parts,components and/or subcomponents and that the present invention is notlimited to automotive applications, in general, nor windshield wiperassemblies, in particular. Furthermore, it will be appreciated that thepresent invention is in no way limited to the specific type of feedstock employed in connection with the manufacture of a beam bladewindshield wiper assembly. Accordingly, the term “feed stock” as usedherein should be given its broadest possible interpretation so as toinclude, for example, but necessarily be limited to: coil stock, platestock, sheet stock, strip stock, tube stock including seamless andseam-welded, round, square, rectangular or any other geometric shape oftube stock, bar stock, cast parts, forged parts, extrusion stock,stamped stock, and wire stock. In addition, those having ordinary skillin the art will readily appreciate that the present invention may alsobe employed in spin-forming operations, roll-forming operations.Similarly, the present invention may also be employed to repair damagedmetal parts and structures, for example, highway and railroad bridgegirders, jet engine components damaged from ingested foreign objects,earthquake damaged building structures, etc. The present invention maybe employed to remove distortion caused by thermal processing such aswelding, brazing, soldering, heat treatments and the like. Those havingordinary skill in the art will also appreciate that the method andapparatus of the present invention may be employed in the forming orrepair of dies for stamping and casting operations, the forming orrepair of molds and pre-forms for fabrication of composite structuressuch as aircraft and spacecraft body and structural members, body andstructural members of boats, ships and the like. In addition, the methodand apparatus of the present invention may be employed to pre-formcomponents in preparation of other forming operations, for example,pre-bending of tubes prior to hydro-forming operations. The presentinvention may also be employed to impart surface modifications such asgrain size reduction, and may also include additional process steps suchas addition heat treatment or hardening. Furthermore, the method andapparatus may be employed in manufacturing operations that require gasand/or powder environments to impart specific surface chemistry to thework piece.

[0053] The invention has been described in an illustrative manner. It isto be understood that the terminology that has been used is intended tobe in the nature of words of description rather than of limitation. Manymodifications and variations of the invention are possible in light ofthe above teachings. Therefore, those having ordinary skill in the artwill appreciate that within the scope of the appended claims, theinvention may be practiced other than as specifically described.

We claim:
 1. An apparatus for manufacturing a discrete curved productfrom a feed stock, said apparatus comprising: a source of heat that isadapted to impose a focused beam of heat on at least one surface of awork piece to cause the surface of the work piece to expand and therebymove in the general direction of the heat source and impart apredetermined radius of curvature to the work piece.
 2. An apparatus asset forth in claim 1 wherein said source of heat imposes a beam of heathaving substantially an oval shape such that the beam shape defines amajor axis and a minor axis and wherein said beam of heat substantiallytraverses the surface of the work piece.
 3. An apparatus as set forth inclaim 1 wherein said source of heat imposes a beam of heat definingsubstantially a line of heat extending substantially transverse to atleast one surface of the work piece.
 4. An apparatus as set forth inclaim 1 wherein said source of heat is a laser that produces a diffusebeam of light directed toward at least one surface of the work piecethereby heating the work piece and causing the surface to expand suchthat the work piece moves in the direction of said laser therebyimparting a predetermined radius of curvature to the work piece.
 5. Anapparatus as set forth in claim 1 wherein said source of heat is a watercooled, plasma, infrared lamp that produces a beam of light directedtoward at least one surface of the work piece thereby heating the workpiece and causing the surface to expand such that the work piece movesin the general direction of said infrared lamp thereby imparting apredetermined radius of curvature to the work piece.
 6. An apparatus asset forth in claim 1 further including a cooler adapted to cool the workpiece after it has been heated by said source of heat.
 7. An apparatusas set forth in claim 6 wherein said cooler is disposed so as to coolthe work piece adjacent to the point of impingement of the focused beamof heat on the surface of the work piece.
 8. An apparatus as set forthin claim 1 further including a tempering device employed to temper thework piece after it has been cooled.
 9. An apparatus as set forth inclaim 8 wherein said tempering device is a second source of heatdisposed in non-contacting relationship to the work piece.
 10. Anapparatus as set forth in claim 8 wherein said tempering device is alaser that impinges a beam of light on the work piece thereby temperingthe work piece.
 11. An apparatus as set forth in claim 10 wherein saidtempering device is a pair of opposed direct diode lasers that impart apair of defocused laser beams onto the work piece.
 12. An apparatus asset forth in claim 8 wherein said tempering device is an infrared lamp.13. An apparatus as set forth in claim 8 wherein said tempering deviceis a water stabilized plasma infrared lamp.
 14. An apparatus as setforth in claim 1 further including a plurality of sensors thatoperatively sense predetermined parameters of the work piece as thepredetermined radius of curvature is imparted thereto and a neuralnetwork coupled to said plurality of sensors, said neural networkadapted to receive data sensed by said plurality of sensors, to comparethe sensed data with stored data and to generate signals to said sourceof heat thereby operatively controlling same.
 15. An apparatus formanufacturing a discrete curved product from a feed stock, saidapparatus comprising: a source of heat that is adapted to impose afocused beam of heat on at least one surface of a work piece, said beamof heat defining a major axis and a minor axis on the work piece wherethe major axis of said focused beam of heat is disposed substantiallytransverse to the relative movement of the work piece with respect tothe beam of heat, said transverse focused beam of heat imparting apredetermined radius of curvature about said major axis.
 16. Anapparatus as set forth in claim 15 wherein said source of heat imposes abeam of heat having substantially an oval shape such that the beam shapedefines a major axis and a minor axis and wherein said beam of heatsubstantially traverses the surface of the work piece.
 17. An apparatusas set forth in claim 15 wherein said source of heat imposes a beam ofheat defining substantially a line of heat extending substantiallytransverse to at least one surface of the work piece.
 18. An apparatusas set forth in claim 15 wherein said source of heat is a laser thatproduces a diffuse beam of light directed toward at least one surface ofthe work piece thereby heating the work piece and causing the surface toexpand such that the work piece moves in the direction of said laserthereby imparting a predetermined radius of curvature to the work piece.19. An apparatus as set forth in claim 15 wherein said source of heat isa water cooled, plasma, infrared lamp that produces a beam of lightdirected toward at least one surface of the work piece thereby heatingthe work piece and causing the surface to expand such that the workpiece moves in the general direction of said infrared lamp therebyimparting a predetermined radius of curvature to the work piece.
 20. Amethod of manufacturing a discrete curved product from a feed stock,said method comprising the steps of: providing a focused beam of heat onat least one surface of a work piece to cause the surface of the workpiece to expand and thereby move in the general direction of the heatsource and impart a predetermined radius of curvature to the work piece.21. A method as set forth in claim 20 further including the step ofcooling the work piece immediately after it has been heated by thesource of heat.
 22. A method as set forth in claim 21 further includingthe steps of tempering the work piece after it has been cooled.